The present invention relates in general to semiconductor integrated circuit devices; and, more particularly, the invention relates to a technique that is effective when applied to a connecting portion between interconnects in a semiconductor integrated circuit device.
In recent years, in view of the tendency toward miniaturization and multi-layering of the interconnects of semiconductor integrated circuit devices (semiconductor devices), studies have been made of the so-called damascene technique for forming a trench in an insulating film and embedding it with a conductive film, thereby forming an interconnect.
This damascene technology can be roughly divided into the single damascene technique and the dual damascene technique. In the former one, a wiring trench and a trench for connecting interconnects are embedded in different steps, while in the latter one, a wiring trench and a connecting trench are embedded simultaneously.
As a conductive film to be filled in such a trench, a copper film or the like is employed. Inside of this trench, a conductive film having barrier properties is formed in order (1) to prevent diffusion, in an insulating film, of a metal constituting the conductive film to be embedded (the metal is copper when the conductive film is a copper film), or (2) when an insulating film is composed of an oxide, such as silicon oxide film, to prevent oxidation of the conductive film, which will otherwise occur owing to the contact between the silicon oxide film and the conductive film.
Over the conductive film (for example, copper film) to be embedded in the trench, an insulating film having barrier properties, such as a silicon nitride film, is formed to prevent diffusion of the metal into the insulating film to be formed over the conductive film or to prevent oxidation thereof by the insulating film.